1. Field of the Invention
This invention relates to the field of form readers, and in particular to a reader for discriminating information on manually marked forms such as lottery entry tickets as well as printed forms such as issued lottery entry validation tickets. The form is advanced by a drum feeder including a stepping motor, past an array of linearly arranged charge coupled device (CCD) light sensors. The outputs of the CCD light sensors are digitized for each step of the motor to obtain a two dimensional image of the form for analysis.
2. Prior Art
Forms for recording handwritten marks for entry of data into a data processing system generally have a plurality of discrete areas arranged in a pattern delineated by background printing on the form. The user indicates a choice by placing a line, an "X" or other mark (e.g., entirely filling in the area) in one of a series of areas presented for choice. Each of the areas is typically defined by a box, oval, pair of spaced lines, etc., and the form normally has a field for a number of such choices. Forms of this type are used for example to encode a lottery player's choice of numbers for a wager, using a form reader in data communication with a lottery agent terminal and with a central lottery computer.
Upon validation of a player's entry the lottery agent terminal prints an entry ticket showing the player's entry and a serial number or other unique identification. The unique identification may include printed alphanumeric characters as well as barcode, optical character recognition (OCR) characters and/or darkened blocks in a geometric pattern representing numeric data. If the player presents a printed ticket as a winning ticket, the lottery agent enters data from the ticket into the terminal for verification by the lottery central computer over the data communication link. This data can be read automatically in the same manner as a handwritten entry form, using an appropriate scanner.
Hand-marked forms are read automatically to determine whether a mark is present or absent in each of the areas presented for choice, normally in rows and columns. Printed forms are examined for the character of printed marks in a given field. The form is illuminated and the level of light reflected from the form is compared to a threshold level. For a row and column form a photocell can be oriented to read each of a number of rows of delineated areas or tracks. The level of reflected light along a track on the form is related in time or position to the pattern which was printed on the form to define the columns, such that a two dimensional array of marks (or missing marks) are determined to be present on the form. In order to correctly reference the position on the form with the level of reflected light and obtain meaningful data, the form must be properly positioned and fed such that either the rows or the columns are aligned to the sensing photocells, and the form is properly fed past the photocells such that by time or position the reflected light signals are accurately related to position on the form. Bar code scanners and OCR readers are similar in that the reflectance of the form in the area of interest is decoded to obtain information from the variations in darkness of the form.
Certain problems are encountered in attempting to obtain accurate data in a form reader, particularly at relatively higher speeds, due to the various parameters which may vary in the form and in the reading process. A form can be misaligned to the feeder; the handwritten or printed marks can vary in character and darkness; the illumination source can vary with aging; the printed delineations can vary in their position on the form; the card can flutter transversely as it is fed along its length, thereby varying the reflectance level due to changes in the distance between the marks and the sensors, etc.
To solve these and other problems, the prior art has provided a number of specific electric and mechanical means for handling the forms. To improve correlation of the signal to position on the form, for example, clocking marks can be printed on the form to trigger the threshold detector. To better respond to the light reflectance variations representing marks, the threshold level of the comparators can be varied adaptively. The form feeding apparatus can be made to high tolerance, and the forms can be printed to high tolerance in delineating the areas for potential marks. These procedures add to the cost and complexity of form production and form reading apparatus.
In U.S. Pat. No. 4,724,307--Dutton et al, an array of charge coupled devices (CCDs) is used to sample and hold a two dimensional representation of the reflectance level over the full face of a form. The form is illuminated at a read station. The reflected image is focused on a two dimensional array of discrete CCD sensors, and the image is parallel loaded into the CCDs all at one time, charging each of the CCD sensor elements to a level which represents the level of reflected light at a corresponding area of the form. The charge levels of the sensors are then read out and digitized, providing a pixel map or numerical representation of the image of the form.
The correlation of the sensor data to the presence or absence of marks includes finding reference marks in the image and searching the data for contrasting edges at predetermined positions in the two dimensional image relative to the reference marks. The individual CCD elements define picture elements (pixels) which are substantially smaller than the mark areas defined by printing on the form. By comparing several neighboring pixels, contrasting edges are detected notwithstanding variations in mark darkness. The processor need only search small areas of the image for the reference marks, and when located, the positions of the reference marks accurately define the positions of all expected marks delineated on the form by printing. Moreover, the mark positions need not define rows and columns.
The device is insensitive to many of the variations which make it difficult to read data in prior art form readers. Due to recording a freeze frame two dimensional image, the reader is insensitive to form feed variations such as variations in feed rate, form alignment and relative distance between the form and the source of illumination and/or the detection devices as occurs with form flutter.
However the form reader according to Dutton et al, as a practical matter, requires all the elements of a video camera to obtain the freeze frame image which is digitized and analyzed. The two dimensional CCD array and the associated optics for focusing the image of the full form on the CCD array make the apparatus relatively expensive compared for example to a line of photocells for each row or column. Moreover, either the form must be advanced to the read station and stopped, or strobed illumination is needed to prevent smearing of the image. These requirements further add to the expense of the reader, and to some extent make the reader less convenient for the user.